Detector-oscillator circuit



July 14, 1936.

F. B. sToNE DETECTOR OSCILLATOR CIRCUIT Filed March .'51, 1934 f. Tone@VMM 2 Sheets-Sheet 1 #TTD/ENE.

July 14, 1936. B, STQNE 2,047,653

DETECTOR osCILLAToR CIRCUIT Filed March 51, 1934 2 sheets-sheet 2llllllll Patented July 14, 1936 UNITED STATES PATENT CFFICEDETEctroR-oscirmr'ron `.entourer Fred B. Stone, Haddon Heights, N. J.,assignor to Radio Corporation of Americana corporation of Delaware Thepresent invention relates to combined detector-oscillator circuits forradio receiving apparatus andthe like, wherein a single electricdischarge device contains, in a common envelope,

electrodes adapted for connection with an oscillator circuit and otherelectrodes adapted for connection with a detector or an amplifiercircuit, the arrangement of the electrodes being such that the twocircuits are coupled through the common lo electronic stream of thedevice.

A- combined detector and oscillator system of the type to which the'invention relates is shown and described in a co-pending application ofJ. C.

A Smith, Serial No. 654,421, filed January 31, 1933, i entitledSignaling systems and assigned to the same assignee as this application.

In said co-pending application a multi-electrode electric dischargedevice, as a combined detector and oscillator, is provided with acathode,

ige an inner control grid as an oscillator grid, a second grid orelectrode adjacent thereto as an oscillator plate, an outer control gridto which signals are applied, a screen electrode for said outer controlgrid, and an output anode to which is 2b connected an intermediatefrequency amplifier. oscillations applied to the inner control grid andsignals applied to the outer control grid are mixed by electroniccoupling and appear in the output lanode circuit as intermediatefrequency signals. 3o With the advent of multi-electrode, dual-functionvelectric discharge devices such as oscillatordetectors of the abovetype, known commercially as pentagrid converters of the general typerepresented by the RCA 6A7 tube, the desirability of utilizing -suchvdevices in other circuits of radio or amplifier apparatus for adifferent purpose, or in the same circuit for a different purpose hasbecome evident. V

In a superheterodyne radio receiver, for exam- 40 ple, it may often beadvantageous to provide a lcircuit and means for utilizing adetector-oscillator, converter or frequency changer type of combinationelectric discharge device, rst normally as a radio signal detector andoscillator and then '45 as an amplifier, such vas an audio frequencyamplifier, for the amplification of signals derived from a phonographpickup device. By employing the same electric dischargedevice as acombined signal detector and oscillator or converter and as an amplifierVfor phonograph signals, it has been found that radio-phonographcombination apparatus of the superheterodyne type may beconsiderablysimplified and reduced in cost.

It is, therefore, an object of the invention to provide a circuit andmeans for utilizing an electric discharge device of the combination typeof a normal function as a signal converter and effectively for differentfunctions in the same or another circuit of radio apparatus and thelike.

Since a device of the character described em- 5 bodies Voscillatorelectrodes and is connected normally with an oscillator circuit havingelectronic coupling with the amplifier or detector portion, theprovision of circuits and switching operations for effectively utilizingthe device and in control- 10 ling the device for providing theadditional functions as above described has been found to present newproblems and difficulties in the way of stable operation.

It is, therefore, a further object of the invention to provide animproved selector circuit for controlling an electric discharge deviceof the combined detector-oscillator type whereby the same may beemployed in other circuits of an apparatus and/or in another mannerwithout appreciably affecting the eciency of operation of thedeviceunder any selected condition of operation.

It is a further object of the present invention to provide an improvedswitching circuit for a combined `detector-oscillator electric dischargetube whereby the same may be employed normally as a detector-oscillatorand alternatively as an amplifier.

It is a still further object of the invention to provide an improvedaudio frequency or phonograph input circuit and switching meanstherefor, whereby the detector elements of `a combineddetector-oscillator electric discharge device may provide an audiofrequency amplifier without being affected by operation of theoscillator portion thereof. Y

It is another object of the invention to provide, in connection with anelectric discharge device of the pentagrid converter type, an improvedsignal 40 receiving circuit and means therein for selectively operatingsaid device as a combined detectoroscillator for continuous wave signalsand as a detector for modulated signals. l

It is also a further object of the invention to provide an improved andsimplified radio phonograph combination system embodying substantially a`minimum number of electric discharge devices and a combined detectoroscillator device having an improved and simplified input couplingcircuit for radio and phonograph signals and an improved output couplingcircuit therefor.

The invention will be better understood, and other objects andadvantages of the invention will appear from the following descriptionwhen considered in connection with the accompanying drawings, and thescope of the invention will be pointed out in the appended claims.

In the drawings, Figure l is a circuit diagram of a combineddetector-oscillator system embodying the invention and arranged forutilizing a portion of the detector-oscillator device as an amplier;

Fig. 2 is a similar circuit diagram of a detectoroscillator systemshowing a modification of the invention as adapted to provide a detectorfor continuous and modulated Wave signals; and

Fig. 3 is a circuit diagram of a radio receiving system and phonographcombination provided with an improved detector-oscillator circuitembodying a further modification of the invention.

Referring to Fig. 1, 5 is a combined detectoroscillator electricdischarge device having a cathode 6 of the heater type, an inner controlgrid 1 connected with a tuned oscillator circuit 8, and an oscillatoranode electrode 9, coupled to the oscillator circuit 8 through anoscillator plate circuit I and a feed-back winding II, the latter beinginductively coupled to the tuned circuit 8.

The cathode 6 is provided with a self-bias resistor I2 inserted incircuit therewith to the negative end of which resistor an outercontrol, or signal grid, I3 is returned through signal input circuits I4and I5. In the present example the signal input circuits are arranged inseries with each other with the circuit I5 more adjacent to the cathode.

The device 5 is provided with an output or main anode I6, in the outputcircuit I'I of which are connected output circuits I8 and I9,corresponding to the input circuits I4 and I5. The device is alsoprovided with a screen electrode between the signal grid I3 and theadjacent electrodes 9 and I6.

Suitable operating potentials for the anode and screen electrodes areobtained from supply terminals 2I providing a source of direct currenthaving a polarity as indicated. An intermediate potential is providedfor the screen electrode 20 through a voltage divider resistor 22connected between the terminals 2| and provided with a tap 23 for thescreen grid supply lead 24.

In the ordinary course of operation radio frequency signals are suppliedthrough the input circuit I4 to the signal control grid I3, whileoscillations are applied to the grid I to provide the desiredintermediate frequency signal, which is taken through the output anodecircuit I'I and the output circuit I8.

In circuit with the oscillator anode 9 is a resistor 25 which isnormally short-circuited by a switch indicated at 26, in the closedposition. With the switch 26 closed, a normal operating potential isapplied to the oscillator anode 9, which is relatively higher than thatapplied to the screen grid 20 from the tap 23. The value of the resistor25 is such that with the switch 26 open, the voltage applied to theoscillator anode is then reduced to a value preferably below that of thescreen grid 20.

It has been found that such reduction of the voltage on the oscillatoranode is sufiicient to stop the oscillations, and that with theoscillations stopped in this manner, the device 5 may be used for otherpurpose than its normal function as a combined detector and oscillator.

It will be noted that the device comprises the oscillator portionincluding the electrodes 6, I and 9, and a screen grid amplifier portionincluding the electrodes 6, I3, I6 and 20. It has been found that bystopping the oscillations, either the In the present example, audiofrequency input A and output circuits are indicated respectively at I5and I9, and in the circuits shown, are provided for the purpose ofutilizing the detector portion as an audio frequency amplier. It will benoted that the circuits I5 and I9 are located at the low frequency endsof the control grid and anode circuits, and when signals are applied tothe device 5 through the input circuit I5, the circuit I4 in seriestherewith offers no appreciable impedance to the low frequency signals.Likewise, the high frequency output circuit I8 offers no appreciableimpedance to the audio or low frequency signals received through theoutput circuit I9 in series therewith.

In order, however, that the low frequency input and output circuits maynot interfere with the transfer of high frequency signals, the circuitsI5 and I 9 are by-passed by any suitable means, such as a condenser ofsuitable value or short circuited by a switch. In the output circuit, acondenser 21, having a low impedance to high frequency signals isemployed in the present example and the low frequency input circuit I5may likewise be by-passed, a suitable switch 28, which is normallyclosed along with the switch 26, being shown by way of example insteadof a condenser.

When the detector-oscillator device is to be used as an amplifier forlow frequency or audio frequency signals, the switch 26 is opened,causing the oscillations to stop and the switch 28 is opened to admitaudio frequency signals to the control grid I3. The amplified audiofrequency signals are received through the output circuit I9. Normaloperation is restored by closing the switch 26 and the switch 28. Theswitches may be arranged for simultaneous operation through a commonoperating means indicated at 29.

While any suitable coupling means may be employed in the input andoutput circuits, in the present example, the input circuit I4 isprovided with a radio frequency tuned input transformer 3|] providedwith signal input terminals 3| and the output anode circuit is similarlyprovided with a suitable intermediate frequency tuned output transformer32 having output terminals indicated at 33.

The audio frequency input and output circuits are provided with suitableaudio frequency coupling transformers indicated at 34 and 35, to whichare connected audio frequency input and output terminals 36 and 31respectively.

For use in connection with a detector-oscillator or pentagrid convertertube of the type represented by the RCA 6A'7, it has been found thatwith normal operating potentials, a resistance of substantially 300,000ohms is suitable for the resistor 25 to effectively stop theoscillations. In any case, however, the oscillations are effectivelystopped by the use of a series resistor in the oscillator plate circuitsufficient to reduce the plate voltage well below that of the screengrid. At the same time, the resistor, being inserted in series with theanode circuit, serves to reduce the energy transfer from the plate tothe grid circuit of the oscillator, and thereby functions in a dualcapacity.

It will be noted that, by this method of stopping oscillations, theoscillator plate circuit is not opened but merely the plate voltage isreduced It has been found that if the plate .circuit is entirely opened,leaving the oscillator plate free, an undesirable effect may be producedin the other associated circuits because of unstable current and voltageconditions on the other elements of the tube.

Accordingly, the preferred method of stopping the oscillations is byincreasing the resistance of, but not opening, the oscillator platecircuit, the resistance being increased, preferably, by the insertion ofa resistor sufficient to simultaneously reduce the oscillator platevoltage below the screen grid voltage and to reduce the energy transferfrom the oscillator plate circuit to the oscillator grid circuit.

It will therefore, be seen that, in the system described, means areprovided to maintain the oscillator .section energized but notfunctioning to produce oscillations, thereby making it possible toutilize one of the sections of the device for other purposes such assignal amplication. Stated generally, this is done by stopping theoscillations in such a manner and by such means that both sections, andparticularly that one to be used for such other purpose, is maintainedunder stable voltage and current conditions. As above described, this isaccomplished by the insertion of a suitable resistance in series withthe oscillator plate. The lowered oscillator plate voltage together withthe reduced energy transfer to -the grid circuit stops the oscillation.The resistor at the same time limits the current to the oscillatorplatethereby preventing objectionable increase in this current.

The oscillations may be stopped, however, by short-circuiting one of theoscillator circuits such as the plate or grid circuit. It has beenfound, however, that .any system which stops the oscillations withoutremoving orlimiting the oscillator plate voltage results in excessiveoscillator plate current unless the combined detector-oscillator deviceis provided with other means of limiting the plate current such as selfbias means. In the case of .self bias means, the increased current isutilized to provide increased bias on the control grid whereby thedevice may be utilized as a high biaseddetector. A system of this.character is shown in Fig. 2, to which attention is now directed andwherein the same reference numerals are used to designate like parts asin Fig. 1.

In the circuit of Fig. 2, the combined detectoroscillator device 5. isarranged to receive either modulated or continuous wave signals throughthe input circuit i4 and to deliver resulting audio frequency signalsthrough the output terminals 31.

The .oscillator plate circuit is provided with a short circuiti'ng meanssuch as a switch 38, and a series resistor 39 is connected in serieswith the oscillator anode to provide the desired anode voltage. Thesupply voltage is sufficiently high and the value of the resistor 39 .issufficiently low to permit oscillations to continue as long as theswitch 38 is open.

When the switch` 38 is closed, the oscillations are stopped, and sincethe oscillations provide the grid bias, the plate current increases to aValue determined by the self bias resistor and to a limited extent bythe anode resistor 39. The increased anode current serves to increasethe selfbias obtainable from the resistor 12 and the signal control gridI3 receives additional negative biasing potential.

The operation of the circuit shown in Fig. 2 is such that withcontinuous wave -signals received through the input circuit I4, theoscillator is permitted to operate to heterodyne therewith and toprovide an audible beat signal through the audio frequency circuit I9.When the device is to be utilized as a detector of modulated signals,receivable through the circuit I 4, the oscillations are stopped byclosing the switch 38, whereupon the detector receives a sufcientlyincreased bias to operate as a high biased detector and the audiofrequency signal component is thereby delivered to the audio frequencyoutput circuit as in the preceding example. Thus, by stopping theoscillations in the manner described, the combined detector-oscillatormay function first as a detector of continuous wave signals', and thenas a detector of modulated wave signals.

It will be noted that advantage is taken of the fact that by stoppingthe oscillations in the manner shown, the oscillator anode currentincreases, to automatically provide a high biased detector. Therefore,this type of control, whereby one of the oscillator circuits isshort-circuited to stop oscillations, may be utilized whenever anincrease in the anode current is desired to be automatically produced.

Referring now to Fig. 3, a combined detectoroscillator device 4i) of thepentagrid converter type is shown in connection with a simplifiedcombination radio and phonograph system. The device 40 is arranged tooperate normally as a combined detector-oscillator in the radioreceiving system, between a tuned high frequency input amplifier 4I anda detector 42, the latter being of the diode rectifier type. An audiofrequency output amplifier indicated at 43 is provided for supplyingaudio frequency signals to an output sound producing device such as aloud speaker, indicated at 44.

The high frequency amplifier 4l is coupled to a suitable source ofmodulated signals such as an antenna 45 through a tuned input couplingtransformer 4Eand, in turn, is coupled through a second tuned highfrequency coupling transformer lll to the signal input or outer controlgrid i8 of the combined detector-oscillator 5%. The output or main anode4Q of the device il is coupled to the detector 42 through a. suitabletuned intermediate frequency transformer 5i). Intermediate frequencysignals supplied thereby to the detector 42 and are rectified andapplied to an output coupling impedance device 5l in the rectifiercircuit, one side of which impedance device is connected to the groundlead 52 through a lead 53 and the high potential side of which isconnected through an output lead 5d and the contacts 55 and of aselector switch 5l, with the output amplifier device 43 through theusual coupling condenser and grid resistor 53 and il@ respective.- ly.The amplifier i3 is connected to the loud speaker 44 through an outputcoupling transformer Eil.

Any suitable audio frequency amplier may be provided, however, exceptthat it is preferable that it be provided with an input circuit adaptedfor impedance coupling. To provide high arnpliication, however, theamplier device 43 may be of the screen grid pentode type as shown andpreferably, be arranged for self -biased operation as indicated by theself-biased resistor The detector-oscillator device lil is furtherprovided with a screen grid 55 for the control grid 48, an oscillatoranode electrode iid, and an inner or oscillator control grid el adjacentto the cathode 63. The oscillator grid is connected with a tuned gridcircuit 69 through the usual grid Lil) leak and condenser means 'F9-1l,the grid leak being connected to the cathode lead indicated at '52. Inthe cathode leads a pair of closed input terminals 'i9 are provided fora purpose which will hereinafter be described.

The oscillator anode electrode 66 is connected through the oscillatoranode circuit indicated at 14 with a feedback winding i5 inductivelycoupled with the tuned circuit 69 as indicated, for setting uposcillations on the grid Gl in accordance with the tuning of the circuit69.

The tuned high frequency single input circuit provided through the tunedsecondary circuit iii of the transformer 4l is connected through a gridcircuit lead 'il with the ground or common lead 52. The cathode lead 'F2is connected through a lead 'iii with a tap 'E9 on a voltage supplyresistor 80, to the negative end of which the ground lead 52 isconnected, as indicated at Sl.

The supply resistor 3G is provided with input terminals S2 for applyingoperating potentials thereto for the various anode and screen electrodesof the apparatus the present example. The lead 33 is connected with anintermediate tap 94 to supply screen grid potentials to the screen grid65 in common with the device di, and a supply lead 85 provides a directhigh potential for the anode circuits of the apparatus, including thedevice il and a terminal 85, the latter being provided for supplying theanode output circuit 8l through the transformer 59 for the output anode4S, as will hereinafter be described.

As shown in the present example, the output circuit 97 is connectedthrough a terminal te and a supply terminal S9 with a supply leadconnected to the high potential terminal of the supply resistor 89through a pair of series resistors 92 and 9S. The resistor 92 isarranged to be short-circuited, normally, through the contacts 94 and 95of the switch 5l and leads extending thereto as indicated at 95. Aby-pass condenser 97 to ground is provided in conjunction with a tappoint 98 between the resistors 92 and 93.

With the circuit arrangement shown, the anode 4S and the oscillatoranode 5S receive operating current through the series resistors 92 and93, the latter serving as a current limiting resistor when the resistor92 is short-circuited by the switch 5l, as shown. Full operatingpotential may, however, be applied to the main output anode of thedetector-oscillator tube, by removing the connection shown, between theterminals 89 and Sil, and placing it between the terminals 85 and 89.The purpose in this connection will hereinafter be described.

A pair of signal input terminals indicated at 99 are provided in circuitwith the control grid 48, preferably as shown in the grid circuit lead'li and to these terminals is connected a source of audio frequencysignals represented by an electric pickup device HB9, the connectionbeing completed through the usual volume control potentiometer deviceil!! and input leads 92. The leads E92 and the leads 'll are preferablyshielded from electrical disturbances.

The operation of the system shown is as follows: iith the potentialsupply circuits energized and the switch l in the position shown, thephonograph pickup or audio frequency input circuit is renderedineffective by short-circuiting the terminals 99. In the presentexample, this is accomplished by moving the potentiometer device ll tothe zero volume position.

'Ihe detector-oscillator device 49 receives nor- 'mal operatingpotential on the oscillator anode 66 through the resistor 93 from thesupply terminals 82 and received modulated signals are rectied by thedevice 42 and supplied through the lead 54 to the audio frequencyamplifier 43, as hereinbefore described.

When the system is desired to function as a phonograph amplier, theswitch 5l' is moved to the alternative position in which the contacts 5Sand S4 are connected together, leaving the contact 55 open and thecontact 95 is connected to the blank contact indicated at |03.

This switching operation serves to remove the short circuit from theresistor 92, thereby reducing the operating anode potential on theoscillator anode 66 and, incidentally, from the main output anode 49.The resistance offered by the resistor 92 is suincient to stop theoscillations. Since the resistor 92 is also inserted in the main outputanode circuit, it serves as a load impedance for that circuit, and thejunction point between the resistor 92 and the plate or main outputanode 49, as indicated at |04, is then coupled through one of the leads96 and the contacts 94 and 56 of the switch 5'! to the audio frequencyamplier.

With this arrangement, when audio frequency signals are supplied to theterminals 99, as by operation of the electric pickup device |90, andwith proper adjustment of the volume control potentiometer lill, theaudio frequency signals are applied to the input signal grid 48 throughthe grid lead il and after amplification are conveyed to the outputcircuit 81 and to the audio frequency amplier 43 in the same manner asradio signals rectified by the rectifier 42.

The switch 5l therefore serves alternatively to connect the audiofrequency output system or amplifier with the signal detector and acoupling impedance inserted in the output anode circuit of thedetector-oscillator device simultaneously therewith by operation of theswitch. Stated in other words, the input circuit of the audio frequencyamplifier comprising the impedance coupling elements 5B and is arrangedfor alternative connection with either the coupling resistor 5I, or theresistor 92 which serves both as a coupling impedance and as a limitingresistor for stopping oscillations of the combined detector-oscillator.By this arrangement, a simplilied circuit and control means for stoppingthe oscillations of and utilizing a combined detectoroscillator deviceas an amplifier are provided.

The biasing potential provided on the control grid i9 is adjusted tosuch a value, between the tap points 19 and 8l on the supply resistor89, that the device 49 may function either as a detector-oscillator oras an amplifier. In the case, however, that it is desired to utilize theoscillator section of the combined detector oscillator device as anamplifier, the audio frequency supply leads H32 are connected to theinput terminals. 73 and the terminals 99 are short circuited in lieu ofthe terminals T3. With this arrangement audio frequency signals areapplied between the cathode and oscillator grid, and the amplied signalsappear in the output circuit 'i4 of the oscillator. Since the oscillatoranode is connected through the coupling impedance 92, the signalsdelivered thereby may be transferred to the audio frequency amplifier byoperation of the switch 5'! in the same manner as hereinbeforedescribed.

In case that the oscillator section is to be utilized continuously as anamplifier instead of the detector section, it is preferable todisconnect the main `output anode circuit from the coupling impedance92. In the present example this is accomplished by disconnecting theterminal 89 from the terminal 9i! andconnecting it to the terminal 86whereupon the main output anode circuit may receive a normal value ofoperating potential, from the positive side of the supply terminals 82through the lead 85.

From the foregoing description it will be seen that by properlyoperating a combined detectoroscillator to stop the oscillations,eitherthe detector or the oscillator section thereof may be utilized asan amplier without interfering with the efficient operation of thedevice in either capacity, and that the same may be carried out by asimple switching operation.

Furthermore, it will be seen that in certain systems, the oscillationsmay preferably be Stopped by inserting resistance in the oscillatoranode circuit and that the inserted resistance in the form of a couplingresistor or impedance may be utilized as a plate or anode circuit loadfor transferring signals to succeeding circuits.

It will also further be seen that the oscillations are in any casepreferably stopped by permitting the oscillator anode circuit to remaincompleted either by short-crcuiting one of the oscillator circuits or byreducing the oscillator anode potential suiilciently to lower it belowthe screen grid potential and to introduce into the oscillator anodecircuit suflicient impedance to lower the energy transferred from theoscillator anode circuit to the oscillator grid circuit.

I claim as my invention:

l. In a signal receiving system, combined detector-oscillator meansincluding in combination, a single electric discharge device having ananode, a cathode, and a plurality of grid electrodes there between, anoscillator circuit connected with and coupling two of said electrodesmore adjacent to the cathode, a signal input circuit connected with.another of said electrodes, means for stopping :oscillations in saidoscillator circuit, and means for utilizing a portion of saiddetector-oscillator means as signal amplifying means.

2. In a signal receiving system, combined detector-oscillator meansincluding in combination, a single electric discharge device having ananode, a cathode, and a plurality of grid electrodes there between, anoscillator circuit connected with and coupling two of said electrodesmore adjacent to the cathode, a signal input circuit connected withanother of said electrodes, means for inserting resistance in circuitwith one of said oscillator electrodes to stop oscillations in saidoscillator circuit, and means for utilizing said cathode, anode andsignal input electrode as a signal amplifier.

3. The combination with an electric discharge device having a cathode,an output anode, a control grid adjacent to the cathode, a secondcontrol grid adjacent to the output anode, a screen grid for said lastnamed control grid and a second anode electrode associated with said rstnamed control grid, of a tuned oscillator circuit connected between thefirst named control grid and the cathode, means for coupling said lastnamed anode to said oscillator circuit to supply oscillations thereto,means for supplying signals to the second named control grid, and meansfor stopping the oscillations in said oscillator circuit whereby saidsignals may be amplified.

4. The combination with an electric discharge device having a cathode,an output anode, a

control grid adjacent to the cathode, a second control gridV adjacent tothe anode, a screen grid for said last named control grid and a secondanode lelectrode associated with said first named control grid, of atuned oscillator circuit connected between the rst named control gridand the cathode, means for coupling said last named anode to saidoscillator circuit to supply oscillations thereto, means for supplyingsignals to the second named control grid, means in circuit with saidlast named anode electrode for reducing operating potentials appliedthereto below the screen grid potential whereby the oscillations in saidoscillator circuit are stopped, and means for utilizing said cathode,second named control grid, screen grid and output anode to amplifysignals while said oscillations are stopped.

5. In a radio receiving system, the combination with a combined detectoroscillator device of the pentagrid converter type, of means for stoppingthe oscillations of said device, and means for utilizing said device toamplify signals while said oscillations are stopped.

6. In a signal receiving system, the combination with a combineddetector-oscillator device of the pentagrid converter type having anoscillator anode, of means for stopping the oscillations of said device,including a current limiting impedance element, and means forselectively inserting said impedance in circuit with said anode toreduce the operating potential thereon to a subnormal value.

7. In a signal receiving system, the combination with a combineddetector-oscillator device of the pentagrid converter type having anoutput anode and a separate oscillator anode, of means for stopping theoscillations of said device, including an impedance element, means forselectively inserting said impedance in circuit with said oscillatoranode to reduce the operating potential thereon to a subnormal value,means for utilizing said impedance in circuit with said oscillator anodeas signal output coupling means for external'signals applied to saiddevice, and means for applying said signals to the input circuit of saiddevice.

8. In a signal receiving system, the combination with an electricdischarge device having a cathode, an anode, a control grid adjacent tothe anode, a second control grid adjacent to the cathode, a screen gridbetween said control grids, and an auxiliary anode electrodeA adjacentto the second control grid, of a signal input circuit connected betweenthe first named control grid and the cathode, said circuit being adaptedto receive continuous wave and modulated signals, a self bias resistorin circuit with the cathode for supplying a biasing potential to saidfirst named grid, oscillator means for heterodyning continuous wavesignals including a tuned grid circuit connected with said secondcontrol grid and an anode circuit coupled therewith and connected withthe auxiliary anode electrode, said circuits being connected with thecathode, a signal output circuit connected with the rst named anode, andmeans for shortcircuiting one of said oscillator circuits when receivingmodulated signals.

9. In a superheterodyne receiver, the combination with an electricdischarge device providing a combined detector-oscillator for saidreceiver and having oscillator grid and anode electrodes, detector gridand anode electrodes and a common cathode for said oscillator anddetector elements, of means for applying audio frequency signals to oneof said grid electrodes, means for inserting an impedance device incircuit With at least one of said anode electrodes including theoscillator anode to stop oscillations therethrough, and means forutilizing said impedance device as a signal output coupling element forsignals applied to said control grid.

10. In a superheterodyne receiver, the combination with an electricdischarge device providing a combined detector-oscillator for saidreceiver and having oscillator grid and anode electrodes, detector gridand anode electrodes and a common cathode for said oscillator anddetector elements, of means for applying audio frequency signals to oneof said grid electrodes, a series impedance device for at least one ofsaid anode electrodes including the oscillator anode to stoposcillations therethrough, means for utilizing said impedance device asa signal output coupling element for signals applied to said controlgrids, an audio frequency amplier having a signal input couplingcircuit, and means for simultaneously connecting said impedance devicein said last named circuit and in the oscillator anode circuit.

11. In a radio receiving system, including a single electric dischargedevice having in a common envelope electrodes adapted for connectionwith an oscillator circuit and other electrodes adapted for connectionwith detector and output intermediate frequency amplier circuits, theelectrode arrangement therein being such that the detector andoscillator circuits are coupled through the common electronic stream ofthe device, the combination with said device and associateddetector-oscillator circuits, of an audio frequency amplier, and meansfor simultaneously stopping the oscillations in the oscillator circuitof said device and connecting the audio frequency amplifier with anoutput circuit of said detector-oscillator device.

12. In a radio receiving system, the combination with a combineddetector-oscillator device having a common cathode, oscillator anddetector portions, each comprising a control grid and a plate electrode,of means for limiting the oscillator plate voltage to stop theoscillations of said device, and means for utilizing a portion of saiddevice as a phonograph signal ampliiier While said oscillations arestopped.

13. In a radio receiving system, the combination with a combineddetector-oscillator device having a common cathode, oscillator anddetector portions, each comprising a control grid and a plate electrode,of a signal input grid circuit for said device, means for applyingphonograph signals thereto, means associated with the oscillator circuitfor maintaining said circuit continuous and reducing the oscillatorplate voltage for simultaneously stopping the oscillations therein, andmeans for deriving amplied phonograph signals from an output circuit ofsaid device.

14. 'I'he combination With a combined detectorv oscillator device havinga common cathode, oscillator and detector portions, each comprising acontrol grid and a plate electrode and having signal input andoscillator circuits connected therewith, of means for maintaining saidoscil- .Y

lator circuit continuous at reduced plate voltage to stop theoscillations therein, and means for utilizing one of said circuits forthe amplification and transmission of external signals through saiddevice when the oscillations are stopped.

FRED B. STONE.

